Pipettes are often used in a laboratory environment to obtain a desired amount of liquid from one container and to dispense the liquid into a different container. Pipettes are available in many forms, from graduated glass tubes to disposable plastic tubes, but all generally operate in a similar manner. One end of the pipette is placed in the liquid to be aspirated, usually from above the liquid, and a reduced pressure is provided in the pipette to draw the liquid into the pipette. The reduced pressure can be provided in various ways, such as the through the use of a deformable bulb, an electric pump, a syringe-like plunger, etc. Handheld pipettes are commercially available for use in obtaining and dispensing measured amounts of liquid on a milliliter and microliter scale. Handheld pipettes are operable with one hand, and manual versions typically include a spring-loaded plunger for drawing liquid into a disposable pipette tip. With such pipettes, the user depresses the plunger against the bias of the spring, places an end of the tip in the liquid, and releases the plunger to draw the liquid into the tip. The user then depresses the plunger again to dispense the liquid.
The resolution and volume capacity of micropipettes often determine the minimum volume of fluid mixtures that must be prepared in a given situation. For instance, to create a 1:10 mixture of fluids A and B, the minimum measurable volume of fluid A is typically 0.10 μl using a commercially available micropipette. There is also an inherent error when drawing fluids with a micropipette due to the fluid surface energy, pipette tip geometry, room temperature, humidity, and other factors. The relative error (i.e., the ratio of the volume of liquid actually drawn into the pipette to the volume of liquid desired to be drawn into the pipette) is typically greater for smaller liquid volumes. Thus, in order to minimize the error in a fluid mixture requiring a small fraction of one component, larger volumes are sometimes prepared. This practice can lead to significant waste when relatively small volumes of a mixture are needed for an experiment, which is compounded when expensive reagents are used.